Heat responsive electric switches are used in many different applications to provide selected process controls. By way of example, switches of this type are shown and described in U.S. Pat. No. 4,349,806, the disclosure of which is herein incorporated by this reference. In such switches a heat responsive element, such as a snap acting theremostatic disc, is disposed in a thermally conductive cap which forms part of the switch housing assembly. The cap is placed in heat transfer relation with a surface whose temperature is to be monitored. Selected changes in temperature cause movement of the heat responsive element which is transmitted to a movable contact to cause an electric circuit to open or close in response to the temperature change.
An important factor in the widespread use of thermostatic switches of this type, in addition to their high degree of reliablility, has been the ability to provide the switches at a low cost. This in turn is the result of structure which has low material cost, is conducive to mass manufacturing techniques, is easily assembled and which required little or no calibration.
Among the many applications for which such thermostatic switches are used are ones in which the switches may be subjected to moisture and fluid flow such as when used for refrigeration defrost and ice maker controls. In such applications it is required to provide an effective seal from liquids for the switch. To answer this need, prior art theremostat switches have been sealed by placing them within a sleeve of plastic material extending around the thermally conductive cap and filling the open end of the sleeve through which the electric leads to the switch extend with epoxy material. While this can provide an effective seal, it results in several undesirable limitations. For example the time required for assembly of the completed sealed switch is significantly extended, for example, up to sixteen hours to permit adequate curing of the epoxy. This ties up storage space and requires special holding means for holding the switches while the epoxy is curing. In addition, the extra mass of material provided by the epoxy makes the thermostatic switch respond more slowly to sensed temperature changes, that is, it makes the device less sensitive.
It is an object of the invention to utilize a thermostatic switch which is use ful for a wide variety of applications in order to minimize unit cost through high volume mass manufcturing techniques and yet provide an effective seal for such switch for special applications which is inexpensive and does not significantly affect or degrade the response time of the switch. Another object of the invention is to provide an improved seal for a thermostatic electric switch which takes significantly less time to manufacture than prior art sealed switches. Yet another object of the invention is to provide an effective means to mount a sealed thermostatic switch to various surface configurations whose temperature are to be monitored.